. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. THE POSTCRANIAL SKELETON OF HETERODONTOSAURUS TUCKI 171 distally, these chevrons narrow to a small rod. From the seventh chevron of the first group to the sixth of the second, the distal end of the chevron is antero- posteriorly expanded into a knob. The length of the chevrons decreases pro- gressively from about the ninth. The first chevron preserved on the last block is 20-21 mm long; the fifth behind that is about 18 mm long; and the last complete chevron is still 16 mm long (on the third from las
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. THE POSTCRANIAL SKELETON OF HETERODONTOSAURUS TUCKI 171 distally, these chevrons narrow to a small rod. From the seventh chevron of the first group to the sixth of the second, the distal end of the chevron is antero- posteriorly expanded into a knob. The length of the chevrons decreases pro- gressively from about the ninth. The first chevron preserved on the last block is 20-21 mm long; the fifth behind that is about 18 mm long; and the last complete chevron is still 16 mm long (on the third from last vertebra). If the reduction in chevron length were a linear function, then 15-20 vertebrae would have com- pleted the caudal series if the smallest chevron were 8-10 mm long. Comparisons The total number of presacral and sacral vertebrae in H. tucki (9+12+6) cannot be matched in any of the well-known ornithopods such as Hypsilophodon (9+15+6), Camptosaurus (9+16+4/5), or Iguanodon (11 + 17+6). Only ceratopsians (including Protoceratops), Psittacosaurus and Protiguanodon have a similar sacral and pre-sacral count. As a whole, the vertebral structure of H. tucki resembles that of Hypsilo- phodon most closely, though similarities to the non-ornithopods are frequent. The axis has a structure similar to that of the ornithopods Hypsilophodon and Camptosaurus^ but also to that of Stegosaurus. In the remaining anterior cervicals, H. tucki and Hypsilophodon are quite similar. However, the deeply concave and short posterior cervical centra are not matched in Hypsilophodon but rather in Protoceratops. The morphology of the dorsal vertebrae agrees with that of typical ornitho- pods such as Hypsilophodon, Camptosaurus and Thescelosaurus and with what is known of Fabrosaurus. The dorsals, however, are unlike those of Fig. 9. H. tucki. Caudal vertebrae on second matrix block illustrated in Figure 8. Scale = 5 Please note that these images are extracted from scanned page im
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
